Wood filler?

I had a guy put windows in a rental property I own last year. I didn't see them until last week, the guy is a hack, but it is too late now. I need some kind of wood filler that can be sanded and nailed, any ideas? This will have to fill about 1/4" gaps. TIA

Wood filler?

Wood filler?

If it were me, I would stuff them with newspaper in the middle and use 1/4 x 1 in. strips to plug the gap on the outside. Then if there are small gaps use wood bondo to fill them. That would help stop any moisture and any small drafts.
Just my thoughts.
Good luck.
Edit...
I was thinking a small gap. Sounds like more than a cheap and easy patch.

Wood filler?

I won't be over there until Friday, I will take pics then. This is not gaps, this is just a total hack job. So much for asking for a contractors license and insurance. I don't know how to describe it, a 10 year old with a hammer and nail could have done just as good. Will Post pics when I get them.

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Wood filler?

If it is a large gap I wouldnt use wood filler. Most wood fillers will crack as the wood around it swellls and contracts with seasonal weather. If it painted I would go with a latex caulking. If it is natural, and was a hack job, yo might want to consider just replacing it.